All our service In every point twice done and then done double Were poor and single business to contend Against those honours deep and broad wherewith Your majesty loads our house...

All Lady M is saying in this extract from Act 1, Scene 6, is, even if every act ("point") of serving Duncan that the Macbeths do were done twice, and each of those done twice, it still would be only a "single" (i.e. not a double, or quadruple) service compared with how much service Duncan is doing them. And what service is Duncan doing them? - he is bringing his "honours... deep and broad" to their house, and thereby making them honourable.